A new calcium-sensor based on ion-selective conductometric microsensors--membranes and features

Based on the concept of ion-selective conductometric microsensors (ISCOM) a new calcium sensor was developed and characterized. ISCOM have a single probe, all-solid-state construction and do not need a reference electrode. These sensors are amenable to miniaturization and integration in the true sense of integrated circuit and microsystem technologies. The detection is accomplished by measurement of the bulk conductance Gm of a thin polymeric membrane containing an ion-complexing agent, where the magnitude of Gm can be related to the content of the primary ion in the analyzed solution. Thin-film platinum electrodes forming an interdigitated electrode are used as the transducer to detect the conductivity of the polymeric membrane. Optimization of the membrane composition was carried out by testing different types of calcium-ionophores, polymers, and plasticizers. The sensor characteristics have been investigated. The limit of detection is about 10(-7) mol L(-1). The dynamic range is 10(-6)-10(-1) mol L(-1) with a response time of less than 5 s. These parameters are comparable to those of corresponding potentiometric calcium selective electrodes (ISE). The Ca(2+)-ISCOM demonstrates good practical relevant selectivities against typical interfering ions for biomedical and environmental applications.